DNA repetitive sequences-types, distribution and function: A review

The development and use of molecular markers for the detection and exploitation of DNA polymorphism is one of the most significant developments in the field of molecular genetics. DNA based molecular markers have acted as versatile tools and have found their own position in various fields like taxonomy, physiology, embryology, genetic engineering etc. A major step forward in genetic identification is the discovery that about 30-90% of the genome is constituted by regions of repetitive DNA which are highly polymorphic in nature. Microsatellites are multilocus probes creating complex banding patterns and are usually non-species specific occurring ubiquitously. They form an ideal marker system and are dominant fingerprinting markers and co-dominant STMS (sequence tagged microsatellites) markers. Microsatellites markers have been used successfully to determine the degree of relatedness among individuals or groups of accessions to clarify the genetic structure or partitioning of variation among individuals, accessions, populations and species. Repetitive sequences have been widely used for examining genome and species relationships by in situ and by Southern hybridization.